Anatomy of the Prostate

The prostate is a male sex gland about the size of a walnut. It is just below the bladder and in front of the rectum. Its main purpose is to produce fluid that carries sperm during orgasm. The tube that carries urine, called the urethra, runs through the prostate. This gland needs male hormones, including testosterone, to function. The testicles are the body’s main source of testosterone.

The prostate has three zones. Prostate cancer mostly occurs in the peripheral zone. It’s the zone closest to the rectal wall. During a digital rectal exam (DRE), your doctor can only feel the peripheral zone. Benign prostate hyperplasia (BPH) is a common noncancerous condition. BPH usually occurs in the transition zone. It’s the zone around the urethra. Sometimes, cancer occurs in the transition zone. Cancer can also occur in the central zone. It’s the zone that surrounds the ejaculatory ducts. In most cases, prostate cancer is found in more than one area of the prostate.